client.c

#include "cFunctions.h"

int main(int argc, char *argv[]) {
	char *host = argv[1];// IP address of the server we want to connect to
	char buf[MAX_LINE];// Buffer we will use to send(), recv(), and write()
	char downloadFileStr[MAX_LINE];// String to hold the name of the file that we will create to write downloaded information into
	const char * SERVER_PORT = argv[2];
	char * password = argv[3];
	int s, len, counter = 0, fileReqAmount = 0;
	fd_set readfds;// Create a fileset for file descriptors
	FD_ZERO(&readfds);// Clear the fileset

	if (!argv[1] || !argv[2] || !argv[3]) {
		fprintf(stderr, "C: Incorrect arguments,\nUSAGE: HOST-ADR PORT# PASS -[OPTIONS]\n");
		exit(1);
	}

	// Get all the options if user selected any - Might want to put ints inside of if-statement and instead ask for each mode operation is argc != 3 so it won't give error
	int debugPrint = 0, printFile = 0;
	if (argc != 3) {
		for (int i = 4; i < argc; i++) {
			if (strcmp(argv[i], "-D") == 0) {debugPrint = 1;}
			else if (strcmp(argv[i], "-PF") == 0) {printFile = 1;}
			else if (strcmp(argv[i], "-H") == 0) {printf("C: Usage is as follows -- HOST-ADR PORT# PASS -[OPTIONS]\n");return 0;}
			else {fprintf(stderr, "C: Invalid option '%s'\nC: The valid options are listed in the README.md, continuing with process\n", argv[i]);}
		}
	}

	// Lookup IP and connect to server
	if ((s = lookup_and_connect(host, SERVER_PORT)) < 0) {exit(1);}
	FD_SET(s, &readfds);

	// Receive a verification from server that we gave a valid password
	if (verifyPassword(s, password, buf) == 1) {
		fprintf(stderr, "C: Error verifying password with server, terminating.\n");
		close(s);
		exit(1);
	}

	// Check buff to see what timeout settings server sent along with our password validation and set ours accordingly
	int serverTimeout = 1;
	if (strcmp(buf, "VALID-NT") == 0) {serverTimeout = 0;}

	// Return response to server on whether user wants to receive the list of files available
	printf("C: List available from host with address '%s'\nC: Are you certain you want to download the list from this host? (yes = y, no = n)\n", argv[1]);
	while (1) {
		memset(buf, 0, MAX_LINE);
		fgets(buf, MAX_LINE, stdin);
		buf[1] = '\0';// Correction for new line on fgets getting filename
		if (strcmp(buf, "y") == 0 || strcmp(buf, "Y") == 0) {
			send(s, buf, 1, 0);
			break;
		} else if (strcmp(buf, "n") == 0 || strcmp(buf, "N") == 0) {
			send(s, buf, 1, 0);
			close(s);
			fprintf(stderr, "C: Told server not to send list, terminating\n");
			return 0;
		} else {
			fprintf(stderr, "C: Invalid input: '%s', please type 'y' for yes, or 'n' for no\n", buf);
		}
	}

	// Print the list of files received
	memset(buf, 0, MAX_LINE);
	printf("%s", debugPrint == 0 ? "\n" : " -- Start list --\n\n");
	while ((len = recv(s, buf, MAX_LINE, 0))) {
		write(1, buf, len);
		memset(buf, 0, MAX_LINE);
		if (isReceiving(s, readfds, 0, 500000) == 0) {break;}// If we're not receiving anymore information, break out of the loop and continue
	}
	printf("%s", debugPrint == 0 ? "\n" : "\n -- End list --\n");

	// Build a temporary string to hold the list as we get it from the User and other variables needed
	if (serverTimeout == 1) {printf("C: The server has given us 1 minute till the timeout for choosing files.\n");}
	printf("C: Please choose up to 10 files from the list above and finish by entering a ';;' or an empty line.\n\n");
	char *tempList = malloc(45 * sizeof(char));
	fd_set waitFDS;

	// Get the file names from the User
	while (1) {
		// Wait for activity from stdin (0 in first arguement)
		if (isReceiving(0, waitFDS, 1, 0) == 1) {
			memset(buf, 0, MAX_LINE);
			fgets(buf, MAX_LINE, stdin);
			buf[strlen(buf) - 1] = '\0';
			
			// First we check if we got the command to break out of the loop
			if (strcmp(buf, "") == 0 || strcmp(buf, ";;") == 0) {
				memset(buf, 0, MAX_LINE);
				break;
			}

			// Check if we can add the entered file name to our list given the length constraint of MAX_LIST_LEN
			if ((sizeof(char)*strlen(tempList)) + (sizeof(char)*strlen(buf)) + snprintf(NULL, 0, "%i", fileReqAmount) + 3 < MAX_LIST_LEN) {
				tempList = realloc(tempList, (sizeof(char)*strlen(tempList)) + (sizeof(char)*strlen(buf)) + 3);
				sprintf(tempList + strlen(tempList), ";;%s", buf);
				fileReqAmount++;
			} else {
				fprintf(stderr, "C: Adding that item to the list would exceede the maximum file list length, breaking out and sending list\n");
				break;
			}
		}

		// Increment counter for the seconds in the input loop and check if we need to leave loop
		counter++;
		if (counter == 60 && serverTimeout == 1) {// This denotes the amount of seconds until we leave the loop if applicable
			fprintf(stderr, "C: We were timed out by the server. Terminating.\n");
			exit(1);
		}
		if (fileReqAmount == 10 || strlen(tempList) > MAX_LIST_LEN) {break;}// Check if we meet the break conditions for max list length or item amount
	}
	
	// Now we put the number of items as well as the list itself into a string to hold it
	char fileList[strlen(tempList) + snprintf(NULL, 0, "%i", fileReqAmount) + 1];
	sprintf(fileList, "%i%s", fileReqAmount, tempList);
	free(tempList);

	// Check that client asked for at least one file
	if (fileReqAmount == 0) {
		fprintf(stderr, "C: You didn't select any files from the list to download. Alerting server and exiting.\n");
		close(s);
		exit(1);
	}

	// Send the file request list to the server
	if (debugPrint == 0) {printf("C: We requested %i file(s) from the server, waiting for server response...\n\n", atoi(fileList));}
	else {printf("C: We requested %i file(s) from the server. Our list was '%s' and was %li in length\nC: Waiting for server response...\n\n", atoi(fileList), fileList, strlen(fileList));}
	send(s, fileList, MAX_LIST_LEN, 0);

	// Setup the structures for file names for the next part
	char *ptr = strtok(fileList, ";;"), curFile[MAX_LINE];
	ptr = strtok(NULL, ";;");

	// Go through the file receiving process for each one of the files in list (Receive file verification -> Receive file -> Send file SHA1 -> Receive SHA1 verification)
	for (int i = 0; i < fileReqAmount; i++) {
		// Grab the current file that we should be receiving from the fileList
		strcpy(curFile, ptr);
		curFile[strlen(ptr)] = '\0';

		// Get the server's response to our request 
		if (isReceiving(s, readfds, 3, 500000) == 1) {
			memset(buf, 0, MAX_LINE);
			recv(s, buf, 1, 0);
		} else {// Safety check for no response from server
			fprintf(stderr, "C: No response to file request for '%s'. Terminating.\n", curFile);
			send(s, "INVALID", 7, 0);
			close(s);
			exit(1);
		}

		// If we got an bad or an invalid response from server
		if (strcmp(buf, "y") != 0) {
			fprintf(stderr, "C: We received a %s response from the server for our request of file '%s'. Terminating.\n", (strcmp(buf, "n") == 0 ? "bad" : "invalid"), curFile);
			close(s);
			exit(1);
		}

		// Alert client as appropriate and prepare for downloading the current file
		if (printFile == 1) {printf("C: Valid response from server to request for file '%s', writing file and printing contents\nC: - Receiving file -\n\n", curFile);}
		else {printf("C: Valid response from server to request for file '%s', writing file\n", curFile);}
		strcpy(downloadFileStr, "DF-");
		strcat(downloadFileStr, curFile);
		int bytesReceived = 0, downloadFile = open(downloadFileStr, O_CREAT | O_WRONLY | O_TRUNC, 0644);

		// Build SHA1 structure and initialize so we can use it during transfer
		SHA_CTX ctx;
		SHA1_Init(&ctx);

		// Begin to recv() the file from server
		while ((len = recv(s, buf, MAX_LINE, 0))) {
			write(downloadFile, buf, len);
			SHA1_Update(&ctx, buf, len);// Update the SHA1 as buf keeps getting read() into
			if (printFile == 1) {write(1, buf, len);}// Write file to terminal in debug mode as we recv() it
			bytesReceived += len; 
			memset(buf, 0, MAX_LINE);
			if (isReceiving(s, readfds, 0, 500000) == 0) {break;}// If we're not receiving anymore information, break out of the loop and continue
		}
		if (printFile == 1) {printf("\nC: - End file -\n");}
		printf("C: Finished receiving file '%s' from server. %i bytes received\n", curFile, bytesReceived);
		close(downloadFile);

		// Build structure for the hash and use SHA1_Final() to end
		unsigned char fileHash[SHA_DIGEST_LENGTH];// Reminder: SHA_DIGEST_LENGTH = 20 bytes
		SHA1_Final(fileHash, &ctx);

		// Make hash into a readable string
		char clientSHA1[SHA_DIGEST_LENGTH*2];
		for (int pos = 0; pos < SHA_DIGEST_LENGTH; sprintf((char*)&(clientSHA1[pos*2]), "%02x", fileHash[pos]), pos++);

		// Send out SHA1 of the downloaded file and wait for the server's response for verification
		send(s, clientSHA1, MAX_LINE, 0);
		memset(buf, 0, MAX_LINE);
		if (isReceiving(s, readfds, 3, 500000) == 1) {recv(s, buf, 1, 0);}
		else {// Safety check for no response from server
			fprintf(stderr, "C: No response to SHA1 verification request for '%s'. Terminating.\n", curFile);
			send(s, "INVALID", 7, 0);
			close(s);
			exit(1);
		}

		// Check the status message and report it to the client before finally ending process
		if (strcmp(buf, "y") == 0) {
			printf("C: Good response from server for SHA1 verification, confirmed that our file is valid. Moving on...\n\n");
		} else if (strcmp(buf, "n") == 0) {
	    	fprintf(stderr, "\nC: Bad response from server to our SHA1 of file '%s'. Terminating.\n", curFile);
	    	close(s);
	    	exit(1);
	    } else {
	    	fprintf(stderr, "\nC: Invalid response from server '%s'. Terminating.\n", buf);
	    	close(s);
	    	exit(1);
	    }
	    ptr = strtok(NULL, ";;");// Go to the next token in our list of files that we requested
	}
	printf("C: Final file transfered, ending processes.\n");
	close(s);
	return 0;
}